First description of the Cro-Magnon 1 endocast and study of brain variation and evolution in anatomically modern Homo sapiens
Paleoneurology is an important research field for studies of human evolution. Variations in the size and shape of the endocranium are a useful means of distinguishing between different hominin species, while brain asymmetry is related to behaviour and cognitive capacities. The evolution of the hominin brain is well documented and substantial literature has been produced on this topic, mostly from studies of endocranial casts, or endocasts. However, we have only little information about variations in endocranial form, size and shape in fossil anatomically modern Homo sapiens(AMH) and about the evolution of the brain since the emergence of our species. One good illustration of this limited knowledge is that one of the first fossil H. sapiens discovered, in 1868, that is also one of the oldest well-preserved European specimen has never been studied in what concerns its endocranial morphology. The first aim of this study was to propose a detailed description of the endocranial anatomy of Cro-Magnon 1, using imaging methodologies, including an original methodology to quantify endocranial asymmetries. The second aim was to compare samples of the fossil and extant AMH in order to document differences in the form, size and shape of the endocasts. A decrease in absolute endocranial size since the Upper Palaeolithic was noticeable. Although both extant and older endocrania have the same anatomical layout, we nonetheless found non-allometric differences in the relative size and organization of different parts of the brain. These document previously unknown intraspecific anatomical variations in the H. sapiens brain, demonstrating its plasticity, with some areas (frontal and occipital lobes) having been more subject to variation than others (parietal, temporal or cerebellar lobes). That may be due to constraints to maintain an optimal performance while reducing in size and changing in shape during our recent evolution.